Method and system for dual projector waveguide displays with wide field of view

ABSTRACT

An eyepiece waveguide for an augmented reality display system includes a substrate having a first surface and a second surface and a diffractive input coupling element formed on or in the first surface or the second surface of the substrate. The diffractive input coupling element is configured to receive an input beam of light and to couple the input beam into the substrate as a guided beam. The eyepiece waveguide also includes a diffractive combined pupil expander-extractor (CPE) element formed on or in the first surface or the second surface of the substrate. The diffractive CPE element includes a first portion and a second portion divided by an axis. A first set of diffractive optical elements is disposed in the first portion and oriented at a positive angle with respect to the axis and a second set of diffractive optical elements is disposed in the second portion and oriented at a negative angle with respect to the axis.

This application claims the benefit of priority to U.S. ProvisionalPatent Application No. 63/029,312, filed May 22, 2020, entitled “METHODAND SYSTEM FOR DUAL PROJECTOR WAVEGUIDE DISPLAYS WITH WIDE FIELD OFVIEW,” the entire contents of which is hereby incorporated by referencein its entirety for all purposes.

BACKGROUND OF THE INVENTION

Modern computing and display technologies have facilitated thedevelopment of systems for so called “virtual reality” or “augmentedreality” experiences, wherein digitally reproduced images or portionsthereof are presented to a viewer in a manner wherein they seem to be,or may be perceived as, real. A virtual reality, or “VR,” scenariotypically involves presentation of digital or virtual image informationwithout transparency to other actual real-world visual input; anaugmented reality, or “AR,” scenario typically involves presentation ofdigital or virtual image information as an augmentation to visualizationof the actual world around the viewer.

Despite the progress made in these display technologies, there is a needin the art for improved methods and systems related to augmented realitysystems, particularly, display systems.

SUMMARY OF THE INVENTION

The present invention relates generally to methods and systems relatedto projection display systems including wearable displays. Moreparticularly, embodiments of the present invention provide methods andsystems that provide an extended field of view in comparison withconventional systems. The invention is applicable to a variety ofapplications in computer vision and image display systems.

As described herein, the field of view of an eyepiece waveguide, alsoreferred to as an eyepiece, is increased with respect to conventionaldesigns by using multiple projectors to create sub-displays that form acombined field of view.

According to an embodiment of the present invention, an eyepiecewaveguide for an augmented reality display system is provided. Theeyepiece waveguide includes a substrate having a first surface and asecond surface. The eyepiece waveguide also includes a diffractive inputcoupling element formed on or in the first surface or the second surfaceof the substrate. The diffractive input coupling element is configuredto receive an input beam of light and to couple the input beam of lightinto the substrate as a guided beam. The eyepiece waveguide furtherincludes a diffractive combined pupil expander-extractor (CPE) elementformed on or in the first surface or the second surface of thesubstrate. The diffractive CPE element includes a first portion and asecond portion divided by an axis. A first set of diffractive opticalelements is disposed in the first portion and oriented at a positiveangle with respect to the axis and a second set of diffractive opticalelements is disposed in the second portion and oriented at a negativeangle with respect to the axis.

According to another embodiment of the present invention, an eyepiecewaveguide for an augmented reality display system is provided. Theeyepiece waveguide includes a substrate having a first surface and asecond surface. The eyepiece waveguide also includes a first diffractiveinput coupling element formed on or in the first surface or the secondsurface of the substrate. The first diffractive input coupling elementis configured to receive a first input beam of light and to couple thefirst input beam of light into the substrate as a first guided beam. Theeyepiece waveguide further includes a second diffractive input couplingelement formed on or in the first surface or the second surface of thesubstrate. The second diffractive input coupling element is configuredto receive a second input beam of light and to couple the second inputbeam of light into the substrate as a second guided beam.

Additionally, the eyepiece waveguide includes a diffractive combinedpupil expander-extractor (CPE) element formed on or in the first surfaceor the second surface of the substrate. The diffractive CPE element ispositioned to receive the first guided beam from the first diffractiveinput coupling element, receive the second guided beam from the seconddiffractive input coupling element, outcouple at least a portion of thefirst guided beam over a first range of angles to form a first field ofview of a combined field of view, and outcouple at least a portion ofthe second guided beam over a second range of angles to form a secondfield of view of the combined field of view.

According to a specific embodiment of the present invention, a waveguidedisplay disposed in glasses is provided. The waveguide display includesa first projector, a second projector, a first incoupling grating (ICG)optically coupled to the first projector, and a second ICG opticallycoupled to the second projector. An axis passes through the first ICGand the second ICG. The waveguide display also includes a firstdiffractive region optically coupled to the first ICG and including afirst portion comprising a first set of gratings oriented at a positiveangle with respect to the axis and a second portion comprising a secondset of gratings oriented at a negative angle with respect to the axis.The waveguide display further includes a second diffractive regionoptically coupled to the second ICG and including a first portioncomprising a third set of gratings oriented at 180° minus the positiveangle with respect to the axis and a second portion comprising a fourthset of gratings oriented at −180° minus the negative angle with respectto the axis.

The first display light from the first projector can impinge on thefirst ICG at a non-zero angle of incidence. In some embodiments, thefirst ICG is characterized by a grating period such that a cone of raysincoupled by the first ICG is centered on the axis passing through thefirst ICG and the second ICG. The second ICG can be characterized by thegrating period. In an embodiment, the first set of gratings and thesecond set of gratings are blazed and characterized by decreasedoutcoupling efficiency for light from the first projector. In anotherembodiment, the third set of gratings and the fourth set of gratings areblazed and characterized by decreased outcoupling efficiency for lightfrom the second projector.

According to a particular embodiment of the present invention, a methodof operating an eyepiece waveguide defined by a first region and asecond region is provided. The method includes directing light from afirst projector to impinge on a first incoupling grating (ICG). Themethod also includes diffracting a fraction of the light from the firstprojector into a first portion of the first region of the eyepiecewaveguide, into a first portion of the second region, into a secondportion of the second region, and out of the eyepiece waveguide. Themethod further includes diffracting another fraction of the light fromthe first projector into a second portion of the first region of theeyepiece waveguide, into a second portion of the second region, into thefirst portion of the second region, and out of the eyepiece waveguide.Additionally, the method includes directing light from a secondprojector to impinge on a second ICG. The method also includesdiffracting a fraction of the light from the second projector into thefirst portion of the second region of the eyepiece waveguide, into thefirst portion of the first region, into the second portion of the firstregion, and out of the eyepiece waveguide. The method further includesdiffracting another fraction of the light from the second projector intothe second portion of the second region of the eyepiece waveguide, intothe second portion of the first region, into the first portion of thefirst region, and out of the eyepiece waveguide.

The first region can include a first set of diffractive optical elementsdisposed in the first portion of the first region and oriented at apositive angle with respect to an axis and a second set of diffractiveoptical elements disposed in the second portion of the first region andoriented at a negative angle with respect to the axis. The second regioncan include a third set of diffractive optical elements disposed in thefirst portion of the second region and oriented at 180° plus thenegative angle with respect to the axis and a fourth set of diffractiveoptical elements disposed in the second portion of the second region andoriented at 180° minus the positive angle with respect to the axis. Inan embodiment, the first set of diffractive optical elements comprises afirst set of gratings and the second set of diffractive optical elementscomprises a second set of gratings. The first set of gratings and thesecond set of gratings can be blazed and characterized by decreasedoutcoupling efficiency for light from the first projector. The third setof diffractive optical elements can include a third set of gratings andthe fourth set of diffractive optical elements can include a fourth setof gratings. The third set of gratings and the fourth set of gratingscan be blazed and characterized by decreased outcoupling efficiency forlight from the second projector. In a specific embodiment, the positiveangle is ˜30° and the negative angle is ˜−30°. The first region and thesecond region can form an overlap region and the overlap region can bedisposed at a midpoint between the first ICG and the second ICG. In someembodiments, the light from the first projector impinges on the firstICG at a first non-zero angle of incidence and the light from the secondprojector impinges on the second ICG at a second non-zero angle ofincidence equal to zero minus the first non-zero angle of incidence. Inan embodiment, a first field of view of the first portion of the secondregion is centered at the first non-zero angle of incidence and a secondfield of view of the first portion of the first region is centered atthe second non-zero angle of incidence.

Numerous benefits are achieved by way of the present invention overconventional techniques. For example, embodiments of the presentinvention provide methods and systems that can be used to increase thefield of view of a display and improve the user experience. In anembodiment, the grating period is selected to produce individual fieldsof view that are tiled or partially overlap to produce a combined fieldof view. These and other embodiments of the invention along with many ofits advantages and features are described in more detail in conjunctionwith the text below and attached figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified plan view diagram illustrating an eyepiecewaveguide according to an embodiment of the present invention.

FIG. 2A is a simplified cross-sectional diagram illustrating an eyepiecewaveguide with decreased grating period according to an embodiment ofthe present invention.

FIG. 2B is a simplified cross-sectional diagram illustrating an eyepiecewaveguide with increased grating period according to an embodiment ofthe present invention.

FIG. 3A is a simplified plan view diagram illustrating elements of aneyepiece waveguide with increased grating period and a combined field ofview according to an embodiment of the present invention.

FIG. 3B is a simplified k-space diagram illustrating operation of theeyepiece waveguide illustrated in FIG. 3A for a first set of light raysforming a first portion of a field of view.

FIG. 3C is a simplified k-space diagram illustrating operation of theeyepiece waveguide illustrated in FIG. 3A for a second set of light raysforming a second portion of a field of view.

FIG. 3D is a simplified k-space diagram illustrating operation of theeyepiece waveguide illustrated in FIG. 3A for the field of view.

FIG. 3E is a simplified k-space diagram illustrating operation of theeyepiece waveguide illustrated in FIG. 3A for an alternate field ofview.

FIG. 3F is a simplified plan view diagram illustrating the eyepiecewaveguide shown in FIG. 3A with exemplary light rays according to anembodiment of the present invention.

FIG. 3G is a simplified k-space diagram illustrating operation of theeyepiece waveguide illustrated in FIG. 3A for a combined field of view.

FIG. 4A is a simplified plan view diagram illustrating a multi-projectorwaveguide display utilizing an eyepiece waveguide with increased gratingperiod according to an embodiment of the present invention.

FIG. 4B is a simplified plan view diagram illustrating propagation ofrays from a second projector in the multi-projector waveguide displayillustrated in FIG. 4A.

FIG. 4C is a simplified k-space diagram illustrating operation of theeyepiece waveguide illustrated in FIG. 4A.

FIG. 4D is a simplified flowchart illustrating a method of operating aneyepiece waveguide defined by a first region and a second regionaccording to an embodiment of the present invention.

FIG. 5A is a simplified plan view diagram illustrating a multi-projectorwaveguide display utilizing an eyepiece waveguide with decreased gratingperiod according to an embodiment of the present invention.

FIG. 5B is a simplified k-space diagram illustrating operation of theeyepiece waveguide illustrated in FIG. 5A.

FIG. 6A is a simplified plan view illustrating elements of amulti-projector waveguide display according to an embodiment of thepresent invention.

FIG. 6B is a simplified plan view diagram illustrating propagation oflight rays in a multi-projector waveguide display according to anembodiment of the present invention.

FIG. 7A is a simplified plan view diagram illustrating a six-projectorwaveguide display according to an embodiment of the present invention.

FIG. 7B is a simplified plan view diagram illustrating a singleprojector element of the six-projector waveguide display illustrated inFIG. 7A.

FIG. 7C is a simplified k-space diagram illustrating operation of thesingle projector element illustrated in FIG. 7B.

FIG. 7D is a simplified k-space diagram illustrating operation of thesix-projector waveguide display illustrated in FIG. 7A.

FIG. 8 is a simplified schematic diagram illustrating integration ofglasses and one or more eyepiece waveguides according to embodiments ofthe present invention

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

The present invention relates generally to methods and systems relatedto projection display systems including wearable displays. Moreparticularly, embodiments of the present invention provide methods andsystems that have an extended field of view in comparison withconventional systems. The invention is applicable to a variety ofapplications in computer vision and image display systems and lightfield projection systems, including stereoscopic systems, systems thatdeliver beamlets of light to the retina of the user, or the like.

FIG. 1 is a simplified plan view diagram illustrating an eyepiecewaveguide according to an embodiment of the present invention. Asillustrated in FIG. 1, eyepiece waveguide 100 includes a firstincoupling grating (ICG) 110 and a second ICG 120. A combined pupilexpander-extractor (CPE) element 130 is disposed between first ICG 110and second ICG 120. Eyepiece waveguide 100 can achieve an expanded fieldof view that can be larger than the range of propagation angles that canbe supported in guided propagation modes in the thickness direction ofthe waveguide. As illustrated in FIGS. 2A and 2B, eyepiece waveguide 100has a first surface 132 and a second surface 134. As discussed furtherbelow, different diffractive features can be formed on or in theopposing surfaces 132 and 134 of eyepiece waveguide 100.

First ICG 110 receives a set of input beams 112 from first projector 150(illustrated in FIG. 2A) and second ICG 120 receives a set of inputbeams 122 from second projector 160 (also illustrated in FIG. 2A). Insome embodiments, the input beams can propagate from the projectorthrough free space until they are incident on one of the ICGs. Asillustrated in FIG. 1, set of input beams 112 incident on ICG 110 andset of input beams 122 incident on ICG 120 are angled or tilted withrespect to the z-axis. ICG 110 and ICG 120 diffract the input beams sothat a portion, which may be all, of the input beams enter guidedpropagation modes within eyepiece waveguide 100. The grating lines ofICG 110 and ICG 120 can be oriented so as to direct the diffracted beamsalong the x-axis toward CPE 130.

CPE 130 can include a plurality of diffractive features that exhibitperiod along multiple axes. Thus, CPE 130 may be composed of an array ofscattering features arranged in a 2D lattice. The individual scatteringfeatures can be, for example, indentations or protrusions of any shape.The 2D array of scattering features has associated grating vectors,which are derived from the reciprocal lattice of that 2D lattice. As oneexample, CPE 130 could be a 2D diffraction grating composed of a crossedgrating with grating lines that repeat along two or more directions ofperiod. The diffractive features that make up CPE 130 can have arelatively low diffraction efficiency (e.g., 10% or less). Accordingly,this low diffraction efficiency allows beams of light to be replicatedin a spatially distributed manner in multiple directions as theypropagate through CPE 130.

FIG. 2A is a simplified cross-sectional diagram illustrating an eyepiecewaveguide with decreased grating period according to an embodiment ofthe present invention. The design illustrated in FIG. 2A results inlight incident on one side of the eyepiece waveguide beingpreferentially outcoupled on the same side of the eyepiece waveguide,thereby providing high efficiency as light is not lost duringpropagation across the eyepiece waveguide, but is outcoupled after ashort propagation path. Moreover, image sharpness is maintained as thepropagation distance and number of TIR reflections is reduced. Asillustrated in FIG. 2A, the grating period, which is inversely relatedto the grating pitch measured between grating teeth, is selected suchthat light rays of the set of input beams 122 of a given wavelengthincident on ICG 120 at an angle greater than zero (i.e., tilted withrespect to the z-axis at a positive angle) is incoupled along adirection centered on the negative x-axis. For this grating withdecreased grating period and increased grating pitch, if light, at thegiven wavelength, was incident at normal incidence, the light would beincoupled along a direction tilted up by a positive angle with respectto the negative x-axis. Thus, the decreased grating period utilizes anincoupling grating that is weaker than conventional designs. In otherwords, if a range of in-waveguide angles was associated with incouplingof a range of angles centered on normal incidence, the grating periodwill be decreased such that a range of angles tilted with respect to thez-axis by a positive angle will be incoupled into the same range ofin-waveguide angles.

Accordingly, the cone of angles defined by light rays 122 tilted at anangle ranging from 0° to +50° with respect to the z-axis is incoupledinto eyepiece waveguide 101 and experiences TIR as the cone of anglespropagates down the waveguide. In order to project light that isincident at non-normal angles, projector 160 can be tilted with respectto the eyepiece waveguide, optics can be utilized to introduce anon-normal angle of incidence from a projector oriented normal to theeyepiece waveguide, or the like.

In the embodiment illustrated in FIG. 2A, outcoupling grating 136 has agrating period that matches the grating period of ICG 120. Accordingly,a cone of angles 123 ranging from 0° to 50° with respect to the z-axisare outcoupled from eyepiece waveguide 101. In other words, if a rangeof in-waveguide angles was propagating in the eyepiece waveguide 101,the grating period of the outcoupling grating 136 will be decreased suchthat a range of angles tilted with respect to the z-axis by a positiveangle will be outcoupled from the same range of in-waveguide angles.Although the incoupling and outcoupling are illustrated on opposingsurfaces of eyepiece waveguide 101, this is not required by the presentinvention and incoupling and outcoupling can occur from a same surface.

Similarly, the grating period of incoupling grating 110 is selected suchthat light rays of input beams 112 of a given wavelength incident on ICG110 at a range of angles less than zero (i.e., tilted with respect tothe z-axis at a negative angle) are incoupled along a direction centeredon the positive x-axis. For this grating with decreased grating periodand increased grating pitch, if light, at the given wavelength, wasincident at normal incidence, the light was be incoupled along adirection tilted up by a positive angle with respect to the x-axis.Accordingly, the cone of angles defined by light rays 112 tilted at anangle ranging from 0° to −50° with respect to the z-axis is incoupledinto eyepiece waveguide 101 and experiences TIR as the cone of anglespropagates down the waveguide. In order to project light that isincident at non-normal angles, projector 150 can be tilted with respectto the eyepiece waveguide, optics can be utilized to introduce anon-normal angle of incidence from a projector oriented normal to theeyepiece waveguide, or the like.

In the embodiment illustrated in FIG. 2A, outcoupling grating 138 has agrating period that matches the grating period of incoupling grating110. Accordingly, a cone of angles 113 ranging from 0° to −50° withrespect to the z-axis is outcoupled from eyepiece waveguide 101.

Although the incoupling and outcoupling are illustrated on opposingsurfaces of eyepiece waveguide 101, this is not required by the presentinvention and incoupling and outcoupling can occur from a same surface.

Thus, utilizing two projectors as illustrated in FIG. 2A, the two fieldsof view produced by projector 150 and projector 160 are thus biased by apredetermined angle with respect to the normal to the eyepiecewaveguide, resulting in the illustrated tiled field of view, i.e., acombined field of view 102. Thus, embodiments of the present inventionutilize a waveguide in which the carrying capacity of the waveguide(i.e., based on TIR angles) is fully utilized in conjunction withnon-normal incident light and modification of grating period fromconventional designs to produce tiled fields of view.

Therefore, using designs characterized by a decreased grating period,light injected at an ICG positioned on one side of the eyepiecewaveguide is preferentially outcoupled on the same side of the eyepiecewaveguide to form a sub-display of a combined field of view. Asillustrated in FIG. 2A, light rays 122 defining a cone of angles tiltedat an angle ranging from 0° to 50° with respect to the z-axis areincoupled into eyepiece waveguide 101 and outcoupled as light rays incone of angles 123, forming a first sub-display covering an angularrange from 0° to 50° with respect to the z-axis. Concurrently, lightrays 112 defining a cone of angles tilted at an angle ranging from 0° to−50° with respect to the z-axis are incoupled into eyepiece waveguide101 and outcoupled as light rays in cone of angles 113, forming a secondsub-display covering an angular range from 0° to −50° with respect tothe z-axis. The combined field of view 102 is formed by tiling of thefirst sub-display and the second sub-display to form combined field ofview 102 equal to 100° covering an angular range from −50° to 50°.

Utilizing polymer eyepiece waveguide materials, including polymers withan index of refraction ˜1.75, conventional eyepiece waveguide designscan achieve a field of view of ˜50°. By utilizing the eyepiece waveguidewith increased grating period illustrated in FIG. 2A, a combined fieldof view of up to 100° can be achieved in a tiled configuration usingsymmetric projector tilt to produce a tilt in the incident angle andmatching increases in grating period for the incoupling and outcouplinggratings, resulting in a symmetric tilting of the output light and atiled field of view. Alternatively, a combined field of view rangingbetween 50° and 100° can be achieved in a partially overlappedconfiguration.

Although FIG. 2A illustrates light being incoupled into the eyepiecewaveguide at a given angle and outcoupled from the eyepiece waveguide atthe given angle, this is not required by the present invention. In otherembodiments, the grating period of the incoupling grating andoutcoupling gratings are modified to enable incoupling of a first coneof angles centered at a first angle and outcoupling of a second cone ofangles centered at a second angle different from the first angle. One ofordinary skill in the art would recognize many variations,modifications, and alternatives.

The structure of the gratings utilized in the embodiment illustrated inFIG. 2A can be varied at different regions of the eyepiece waveguide. Inthis design with decreased grating period, blazed gratings can be usedto increase outcoupling efficiency. As an example, gratings 136 can beblazed to increase their efficiency for light received from projector160 and gratings 138 can be blazed to increase their efficiency forlight received from projector 150. This blazed grating design willresult in less light from projector 150 being outcoupled by gratings 136and less light from projector 160 being outcoupled by gratings 138. Inthe central region between gratings 136 and gratings 138, the gratingstructure can be graded to start with one blazed grating profile and endwith the other blazed grating profile with a binary grating in thecentral region. In addition to blazed gratings, other diffractivesurfaces, particularly surfaces that are characterized by differingdiffraction efficiencies depending on the direction of the incominglight, including meta-surfaces and meta-materials, volume phaseholograms, stepped gratings, and the like can be utilized. One ofordinary skill in the art would recognize many variations,modifications, and alternatives.

FIG. 2B is a simplified cross-sectional diagram illustrating an eyepiecewaveguide with increased grating period according to an embodiment ofthe present invention. The design illustrated in FIG. 2B results inlight incident on one side of the eyepiece waveguide beingpreferentially outcoupled on the opposite side of the eyepiecewaveguide. Using designs with increased grating period, the spatialseparation between the incoupling gratings and the outcoupling gratingscan be decreased while providing room for the image size to expand,reducing the size of the eyepiece waveguide. As illustrated in FIG. 2B,the grating period, which is inversely related to the grating pitchmeasured between grating teeth, is selected such that light rays 122 ofa given wavelength incident on ICG 154 at an angle greater than zero(i.e., tilted with respect to the z-axis at a positive angle) isincoupled along a direction centered on the positive x-axis. For thisgrating with increased grating period and decreased grating pitch, iflight, at the given wavelength, was incident at normal incidence, thelight would be incoupled along a direction tilted up by a positive anglewith respect to the positive x-axis. Thus, the increased grating periodutilizes an incoupling grating that is stronger than conventionaldesigns. Accordingly, the cone of angles defined by light rays 122tilted at an angle ranging from 0° to +50° with respect to the z-axis isincoupled into eyepiece waveguide 104 and experiences TIR as the cone ofangles propagates down the waveguide. In order to project light that isincident at non-normal angles, projector 160 can be tilted with respectto the eyepiece waveguide, optics can be utilized to introduce anon-normal angle of incidence from a projector oriented normal to theeyepiece waveguide, or the like.

In the embodiment illustrated in FIG. 2B, outcoupling grating 156 has agrating period that matches the grating period of ICG 154. Accordingly,a cone of angles 123 ranging from 0° to 50° with respect to the z-axisis outcoupled from eyepiece waveguide 104. Although the incoupling andoutcoupling are illustrated on opposing surfaces of eyepiece waveguide104, this is not required by the present invention and incoupling andoutcoupling can occur from a same surface.

Similarly, the grating period of incoupling grating (ICG) 164 isselected such that light rays 112 of a given wavelength incident on ICG164 at a range of angles less than zero (i.e., tilted with respect tothe z-axis at a negative angle) are incoupled along a direction centeredon the negative x-axis. For this grating with increased grating periodand decreased grating pitch, if light, at the given wavelength, wasincident at normal incidence, the light would be incoupled along adirection tilted up by a positive angle with respect to the negativex-axis. Accordingly, the cone of angles defined by light rays 112 tiltedat an angle ranging from 0° to −50° with respect to the z-axis isincoupled into eyepiece waveguide 104 and experiences TIR as the cone ofangles propagates down the waveguide. In order to project light that isincident at non-normal angles, projector 150 can be tilted with respectto the eyepiece waveguide, optics can be utilized to introduce anon-normal angle of incidence from a projector oriented normal to theeyepiece waveguide, or the like.

In the embodiment illustrated in FIG. 2B, outcoupling grating 166 has agrating period that matches the grating period of incoupling grating164. Accordingly, a cone of angles 113 ranging from 0° to −50° withrespect to the z-axis is outcoupled from eyepiece waveguide 104.Although the incoupling and outcoupling are illustrated on opposingsurfaces of eyepiece waveguide 104, this is not required by the presentinvention and incoupling and outcoupling can occur from a same surface.

Thus, utilizing two projectors as illustrated in FIG. 2B, the two fieldsof view produced by projector 150 and projector 160 are thus biased by apredetermined angle with respect to the normal to the eyepiecewaveguide, resulting in the illustrated tiled field of view, i.e., acombined field of view 105. Thus, embodiments of the present inventionutilize a waveguide in which the carrying capacity of the waveguide(i.e., based on TIR angles) is fully utilized in conjunction withnon-normal incident light and modification of grating period fromconventional designs to produce tiled fields of view.

Therefore, using designs characterized by an increased grating period,light injected at an ICG positioned on one side of the eyepiecewaveguide propagates to the other side of the eyepiece waveguide whereit is outcoupled to form a sub-display of a combined field of view. Asillustrated in FIG. 2B, light rays 122 defining a cone of angles tiltedat an angle ranging from 0° to 50° with respect to the z-axis areincoupled into eyepiece waveguide 104 and outcoupled as light rays 123,forming a first sub-display covering an angular range from 0° to 50°with respect to the z-axis. Concurrently, light rays 112 defining a coneof angles tilted at an angle ranging from 0° to −50° with respect to thez-axis are incoupled into eyepiece waveguide 104 and outcoupled as lightrays 113, forming a second sub-display covering an angular range from 0°to −50° with respect to the z-axis. The combined field of view 105 isformed by tiling of the first sub-display and the second sub-display toform combined field of view 105 equal to 100° covering an angular rangefrom −50° to 50°.

Utilizing polymer eyepiece waveguide materials, including polymers withan index of refraction ˜1.75, conventional eyepiece waveguide designscan achieve a field of view of −50°. By utilizing the eyepiece waveguidewith increased grating period illustrated in FIG. 2B, a combined fieldof view of up to 100° can be achieved in a tiled configuration usingsymmetric projector tilt to produce a tilt in the incident angle andmatching increases in grating period for the incoupling and outcouplinggratings, resulting in a symmetric tilting of the output light and atiled field of view. Alternatively, a combined field of view rangingbetween 50° and 100° can be achieved in a partially overlappedconfiguration.

Although FIG. 2B illustrates light being incoupled into the eyepiecewaveguide at a given angle and outcoupled from the eyepiece waveguide atthe given angle, this is not required by the present invention. In otherembodiments, the grating period of the incoupling grating andoutcoupling gratings are modified to enable incoupling of a first coneof angles centered at a first angle and outcoupling of a second cone ofangles centered at a second angle different from the first angle. One ofordinary skill in the art would recognize many variations,modifications, and alternatives.

The structure of the gratings utilized in the embodiment illustrated inFIG. 2B can be varied at different regions of the eyepiece waveguide. Inthis design with increased grating period, blazed gratings can be usedto increase outcoupling efficiency. As an example, gratings 156 can beblazed to increase their efficiency for light received from projector160 and gratings 166 can be blazed to increase their efficiency forlight received from projector 150. This blazed grating design willresult in less light from projector 150 being outcoupled by gratings 156and less light from projector 160 being outcoupled by gratings 166. Inthe central region between gratings 156 and gratings 166, the gratingstructure can be graded to start with one blazed grating profile and endwith the other blazed grating profile with a binary grating in thecentral region. One of ordinary skill in the art would recognize manyvariations, modifications, and alternatives.

FIG. 3A is a simplified plan view diagram illustrating elements of aneyepiece waveguide with increased grating period and a combined field ofview according to an embodiment of the present invention. In FIG. 3A,propagation and diffraction of light rays in the waveguide display areillustrated as well as a resulting field of view. As illustrated in FIG.3A, diffraction of input light by ICG 305 results in light diffractedinto and propagating in the plane of the waveguide as illustrated bylight rays 311 and 315. As will be described, light rays represented bylight ray 311 and light rays represented by light ray 315 will result inthe generation of a field of view 310 (illustrated in FIG. 3D) thatincludes a first portion 310 a and a second portion 310 b.

Light ray 311 propagates up and to the right after diffraction from ICG305 and diffracts from gratings in the top portion of the waveguide,producing light ray 312, which propagates down and to the right. ThisOPE diffraction event is represented by arrow 322 in FIG. 3B. Light ray312 propagates in the waveguide and diffracts from gratings in the lowerportion of the waveguide, producing outcoupling event 313. Outcoupledlight ray 314 is illustrated as propagating up toward the user from thelower portion of the waveguide, thereby producing first portion 310 a offield of view 310, which is associated with the lower portion of theuser's field of view.

Concurrently, light ray 315 propagates down and to the right near axis301 and diffracts from gratings in the lower portion of the waveguidenear axis 301, producing light ray 316, which propagates up and to theright. This OPE diffraction event is represented by arrow 332 in

FIG. 3C. Light ray 316 propagates in the waveguide and diffracts fromgratings in the upper portion of the waveguide near axis 301, producingoutcoupling event 317. Outcoupled light ray 318 is illustrated aspropagating down toward the user from the upper portion of the waveguidenear axis 301, thereby producing lower portion 310 b of field of view310.

Thus, field of view 310 includes first portion 310 a, associated withlight ray 311 as well as second portion 310 b associated with light ray315. As will be evident to one of skill in the art, rays incoupled atintermediate angles and operable to propagate in the waveguide will fillout field of view 310.

FIG. 3B is a simplified k-space diagram illustrating operation of theeyepiece waveguide illustrated in FIG. 3A for a first set of light raysforming a first portion of a field of view. As illustrated in FIG. 3B,the first portion 310 a of field of view 310 travels through the k-spacediagram as represented by positions 326 and 328 so that it is notclipped by the boundaries of the annulus defined by the circlepositioned at n=1.0 and the circle positioned at n=1.75 corresponding tothe in-waveguide angles. Diffraction in the plane of the eyepiecewaveguide and diffraction out of the plane of the eyepiece waveguidethus result in travel in the k-space diagram through regions thatpropagate inside the eyepiece waveguide.

Referring to FIG. 3B, diffraction from ICG 305 is represented by arrow320 representing a grating vector translating the first portion 310 a ofthe field of view to the in-waveguide region of the k-space diagram asillustrated by position 326. The OPE diffraction event resulting fromlight ray 311 diffracting to produce light ray 312 as illustrated inFIG. 3A is represented by arrow 322 in FIG. 3B, translating the firstportion 310 a of the field of view from position 326 in the in-waveguideregion of the k-space diagram to position 328, which is also in thein-waveguide region of the k-space diagram. The EPE outcoupling event313 resulting from light ray 312 diffracting to produce outcoupled lightray 314 is represented by arrow 324 in FIG. 3B, translating the firstportion 310 a of the field of view from position 328 in the in-waveguideregion of the k-space diagram to the eye-space region of the k-spacediagram associated with first portion 310 a of the field of view.

Thus, as indicated by the k-space diagram illustrated FIG. 3B, light inthe lower portion of the user's field of view is formed by light rayspropagating up toward the user from the lower portion of the waveguide,thereby producing first portion 310 a of field of view 310.

The k-space diagram in FIG. 3B demonstrates that the eyepiece waveguidedesign illustrated in FIG. 3A has a grating spacing along axis 302 thatis characterized by an increased grating period since the center offield of view 310 a is translated as a result of OPE and EPE diffractionevent by a distance measured along axis 302 that is greater than thedistance from the origin to the position along axis 302 at which thecenter of the field of view represented at position 328 is located. Inother words, referring to FIG. 3B, the distance L, which is measuredalong axis 302, is greater than the distance D. In comparison,considering the magnitude of the translation along axis 301, thedistance from the origin to point 303 is equal to the distance thecenter of field of view 310 a is translated along axis 301 since thegrating spacing along axis 301 is not characterized by an increasedgrating period or a decreased grating period.

Thus, using eyepiece waveguide designs that include grating linesoriented at ˜60° to each other, light can flow in the k-space diagramalong three different grating vectors: arrow 320 representing a gratingvector aligned with axis 301, which represents diffraction by the ICGinto the plane of the eyepiece waveguide and translates field of view310 a to position 326; arrow 322 representing a grating vector orientedat ˜−120° to axis 301 and translating the field of view at position 326to position 328; and arrow 324 representing a grating vector oriented at˜60° to axis 301 and translating the field of view at position 328 tofield of view 310 a. Since positions 326 and 328 are within the annulusof in-waveguide angles, light diffracted along these three differentgrating vectors will be maintained in the eyepiece waveguide.

FIG. 3C is a simplified k-space diagram illustrating operation of theeyepiece waveguide illustrated in FIG. 3A for a second set of light raysforming a second portion of a field of view. Referring to FIG. 3A, lightray 315, after diffraction from ICG 305, propagates down and to theright near axis 301, eventually resulting in generation of outcoupledlight ray 318. As illustrated in FIG. 3C, diffraction from ICG 305 isrepresented by arrow 330, translating the second portion 310 b of thefield of view to the in-waveguide region of the k-space diagram asillustrated by position 336. The OPE diffraction event resulting fromlight ray 315 diffracting to produce light ray 315 as illustrated inFIG. 3A is represented by arrow 332 in FIG. 3C, translating the secondportion 310 b of the field of view from position 336 in the in-waveguideregion of the k-space diagram to position 338, which is also in thein-waveguide region of the k-space diagram. The EPE outcoupling event317 resulting from light ray 316 diffracting to produce outcoupled lightray 318 is represented by arrow 334 in FIG. 3C, translating the secondportion 310 b of the field of view from position 338 in the in-waveguideregion of the k-space diagram to the eye-space region of the k-spacediagram associated with second portion 310 b of the field of view.

As discussed in relation to first portion 310 shown in FIG. 3B, secondportion 310 b of field of view 310 travels through the k-space diagramas represented by positions 336 and 338 so that it is not clipped by theboundaries of the annulus defined by the circle positioned at n=1.0 andthe circle positioned at n=1.75 corresponding to the in-waveguideangles. Diffraction in the plane of the eyepiece waveguide anddiffraction out of the plane of the eyepiece waveguide thus results intravel in the k-space diagram through regions that propagate inside theeyepiece waveguide.

FIG. 3D is a simplified k-space diagram illustrating operation of theeyepiece waveguide illustrated in FIG. 3A for the field of view. In thek-space diagram illustrated in FIG. 3D, first portion 310 a and secondportion 310 b of the field of view 310 are shown. As discussed inrelation to FIGS. 3A-3C, light rays diffracted into the waveguide by theICG and propagating to the right and generally up, as well as down atsmall angles with respect to axis 301, can be represented in k-space bytranslation of field of view 310 to positions 326 and 336, representingpropagation in the waveguide. OPE interactions represented by arrows 322and 332 represent propagation from an upper portion of the waveguide toa lower portion of the waveguide and propagation from a lower portion ofthe waveguide to an upper portion of the waveguide, respectively.Finally, EPE interactions are represented by outcoupling that isrepresented by field of view 310 at angles in the eye-space region.

Thus, field of view 310 includes first portion 310 a, associated withlight ray 311 as well as second portion 310 b associated with light ray315. As will be evident to one of skill in the art, rays incoupled atintermediate angles and operable to propagate in the waveguide will fillout field of view 310.

FIG. 3E is a simplified k-space diagram illustrating operation of theeyepiece waveguide illustrated in FIG. 3A for an alternate field ofview. In FIG. 3E, field of view 340, which is associated with the lowerportion of the user's field of view, is formed as light propagates downtoward the user from the upper portion of the waveguide. Thus, field ofview 340 is a mirror image of field of view 310 with respect to axis301.

Referring to FIG. 3E, first portion 340 a and second portion 340 b ofthe field of view 340 are shown. In a manner similar to the operationshown in relation to FIGS. 3A-3D, and in a mirror image fashion, lightrays diffracted into the waveguide by the ICG and propagating to theright and generally down, as well as up at small angles with respect toaxis 301, can be represented in k-space by translation of field of view340 to positions 346 and 356, representing propagation in the waveguide.OPE interactions result in translation of the first portion to position348 and translation of the second portion to position 358, respectivelyas these in-waveguide propagation angles are supported by the waveguide.Finally, EPE interactions are represented by outcoupling that isrepresented by field of view 340 at angles in the eye-space region.

Thus, as a mirror image of field of view 310, field of view 340 includesfirst portion 340 a, associated with light rays propagating down and tothe right in FIG. 3A as well as second portion 340 b associated withlight rays propagating up and to the right in FIG. 3A. As will beevident to one of skill in the art, rays incoupled at intermediateangles and operable to propagate in the waveguide will fill out field ofview 340.

FIG. 3F is a simplified plan view diagram illustrating the eyepiecewaveguide shown in FIG. 3A with exemplary light rays according to anembodiment of the present invention. In FIG. 3F, representative lightrays associated with both the first and second portions of fields ofview 310 and 340 are illustrated. As discussed in relation to FIG. 3A,light ray 311 propagates up and to the right after diffraction from ICG305 and diffracts from gratings in the top portion of the waveguide,producing a light ray propagating down and to the right (OPEinteraction). When this light ray interacts with gratings in the lowerportion of the waveguide, an EPE event occurs, resulting in outcouplingof light ray 314 such that it propagates up toward the user from thelower portion of the waveguide, thereby producing first portion 310 a offield of view 310. Concurrently, light ray 315 propagates down and tothe right near axis 301 and diffracts from gratings in the lower portionof the waveguide near axis 301, producing a light ray propagating up andto the right (OPE interaction). When this light ray interacts withgratings in the top portion of the waveguide, an EPE event occurs,resulting in outcoupling of light ray 318 such that it propagates downtoward the user from the top portion of the waveguide, thereby producingsecond portion 310 b of field of view 310.

In a mirror image fashion, light ray 381 propagates down and to theright and diffracts from gratings in the lower portion of the waveguideas an OPE diffraction event, producing light ray 382, which propagatesup and to the right. Light ray 382 propagates in the waveguide anddiffracts from gratings in the upper portion of the waveguide, producingoutcoupling event 383. Outcoupled light ray 384 is illustrated aspropagating down toward the user from the upper portion of thewaveguide, thereby producing first portion 340 a of field of view 340,which is associated with the upper portion of the user's field of view.Concurrently, light ray 385 propagates up and to the right near axis 301and diffracts from gratings in the upper portion of the waveguide nearaxis 301 as an OPE diffraction event, producing light ray 386, whichpropagates down and to the right. Light ray 386 propagates in thewaveguide and diffracts from gratings in the lower portion of thewaveguide near axis 301, producing outcoupling event 387. Outcoupledlight ray 388 is illustrated as propagating up toward the user from thelower portion of the waveguide near axis 301, thereby producing secondportion 340 b of field of view 340.

Thus, field of view 340 includes first portion 340 a, associated withlight ray 381 as well as second portion 340 b associated with light ray385. As will be evident to one of skill in the art, rays incoupled atintermediate angles and operable to propagate in the waveguide will fillout field of view 340.

Also, although only four OPE interactions and four EPE interactions areillustrated for purposes of clarity, it will be appreciated that lightrays 311/385 and 315/381 will experience OPE interactions throughout thetop portion and the bottom portion of the waveguide, respectively.Similarly, light rays 312/386 and 316/382 will experience EPEinteractions through the bottom portion and the top portion of thewaveguide, respectively. Accordingly, outcoupling events will occurthroughout the waveguide and outcoupling events 313/387 and 317/383 aremerely exemplary. As a result, outcoupled light rays distributed acrossthe waveguide will contribute to the generation of fields of view 310and 340.

It should be noted that the gratings in the top and bottom portions ofthe waveguide intersect at axis 301 with no overlap in the embodimentillustrated in FIG. 3F. However, this is not required by the presentinvention and, in some other embodiments, the gratings overlap atpositions along axis 302 at predetermined distances above and/or belowaxis 301. This overlap region will enable rays that are propagating intothe top portion of the waveguide to experience OPE interactions withgrating originating in the bottom portion of the waveguide and extendinginto the top portion of the waveguide in the overlap region. Continuingwith this example, rays that are propagating into the top portion of thewaveguide and experience an OPE interaction in the overlap region willdiffract up into the top portion and can experience an EPE interactionthat will result in an outcoupling event that will enhance the outputassociated with field of view 340. Similarly, light rays that arepropagating into the bottom portion of the waveguide can experience OPEinteractions with gratings originating in the top portion of thewaveguide and extending into the bottom portion of the waveguide in theoverlap region. These rays that are propagating into the bottom portionof the waveguide and experience an OPE interaction in the overlap regionwill diffract down into the bottom portion and can experience an EPEinteraction that will result in an outcoupling event that will enhancethe output associated with field of view 310.

As described in relation to FIG. 3G, utilizing the waveguide designillustrated in FIGS. 3A and 3F, a combined field of view is formed bythe overlap of field of view 310 and field of view 340. Thus, althougheach field of view individually provides a field of view (i.e.,vertical×horizontal) of ˜50°×˜40°, the overlapped fields of view providea combined field of view of ˜80°×˜40°, thereby significantly improvingthe user experience.

FIG. 3G is a simplified k-space diagram illustrating operation of theeyepiece waveguide illustrated in FIG. 3A for a combined field of view.Referring to FIG. 3G, combined field of view 350 is formed by theoverlap between field of view 310 and field of view 340. Althoughtranslation of field of view 310 to positions 360 and 361 is illustratedfor purposes of clarity, it will be appreciated that portions of thisfield of view translate, in k-space, through position 366. Similarly,translation of field of view 340 to positions 365 and 366 is illustratedfor purposes of clarity, it will be appreciated that portions of thisfield of view translate, in k-space, through position 361. Asillustrated in FIG. 3G, field of view 310 has a spatial extent of ˜50°vertically by ˜40° horizontally. Similarly, field of view 340 has asimilar spatial extent. Due to the overlap between these fields of view,a combined field of view characterized by a much larger extended fieldof view of ˜80°×˜40° is formed. Thus, using embodiments of the presentinvention that utilize a single projector and gratings that arecharacterized by an increased grating period in one dimension, waveguidedisplays with an increased field of view are enabled.

FIG. 4A is a simplified plan view diagram illustrating a multi-projectorwaveguide display 400 utilizing an eyepiece waveguide with increasedgrating period according to an embodiment of the present invention. In amanner similar to that discussed in relation to FIG. 2B, diffraction ofinput light by ICG 405 results in light diffracted into and propagatingin the plane of the waveguide as illustrated by light rays 411 and 415.As will be described, light rays represented by light ray 411 and lightrays represented by light ray 415 will result in the generation of afield of view that includes two portions, each associated with lightrays initially propagating into the upper half of the eyepiece waveguideand the lower half of the eyepiece waveguide, respectively.

Multi-projector waveguide display 400 includes a first region 403, whichin this embodiment is circular, and a second region 404, which is alsocircular in this embodiment. First region 403 and second region 404overlap to form overlap region 406. In FIG. 4A, overlap region 406 isdisposed at a midpoint between the ICG 405 and ICG 425. First region 403includes a first portion defined by the upper semicircle of first region403 and a second portion defined by the lower semicircle of first region403. Likewise, second region 404 includes a first portion defined by theupper semicircle of second region 404 and a second portion defined bythe lower semicircle of second region 404. Overlap region 406 is formedby the overlap of the first portion of the first region and the firstportion of the second region and the overlap of the second portion ofthe first region and the second portion of the second region. Additionaldescription related to the eyepiece waveguide of the multi-projectorwaveguide display is provided in relation to FIG. 6A.

Light ray 411 propagates up and to the right after diffraction from ICG405 and diffracts from gratings in the top portion of the waveguide,producing light ray 412, which propagates down and to the right. Lightray 412 propagates in the waveguide and diffracts from gratings in thelower portion of the waveguide, producing outcoupling event 413.Outcoupled light ray 414 is illustrated as propagating up toward theuser from the lower portion of the waveguide, thereby producing aportion of the field of view associated with the lower portion of theuser's field of view.

Concurrently, light ray 415 propagates down and to the right near axis401 and diffracts from gratings in the lower portion of the waveguidenear axis 401, producing light ray 416, which propagates up and to theright. Light ray 416 propagates in the waveguide and diffracts fromgratings in the upper portion of the waveguide near axis 401, producingoutcoupling event 417. Outcoupled light ray 418 is illustrated aspropagating down toward the user from the upper portion of the waveguidenear axis 401, thereby producing a lower portion of the field of view.As will be evident to one of skill in the art, rays incoupled atintermediate angles and operable to propagate in the waveguide will fillout the field of view. Referring to FIG. 4C, field of view 410 isproduced by the light rays illustrated by light rays 411 and 415.

FIG. 4B is a simplified plan view diagram illustrating propagation ofrays from a second projector in the multi-projector waveguide displayillustrated in FIG. 4A. As will be evident to one of skill in the art,the operation of the eyepiece waveguide discussed in relation to FIG. 4Bwill mirror, to some extent, the operation of the eyepiece waveguide asdiscussed in relation to FIG. 4A. Namely, diffraction of input light byICG 425, which originates with a second projector (not shown), resultsin light diffracted into and propagating in the plane of the waveguideas illustrated by light rays 431 and 435. As will be described, lightrays represented by light ray 431 and light rays represented by lightray 435 will result in the generation of a field of view that includestwo portions, each associated with light rays initially propagating intothe upper half of the eyepiece waveguide and the lower half of theeyepiece waveguide, respectively.

Light ray 431 propagates up and to the left after diffraction from ICG425 and diffracts from gratings in the top portion of the waveguide,producing light ray 432, which propagates down and to the left. Lightray 432 propagates in the waveguide and diffracts from gratings in thelower portion of the waveguide, producing outcoupling event 433.Outcoupled light ray 434 is illustrated as propagating up toward theuser from the lower portion of the waveguide, thereby producing aportion of the field of view associated with the lower portion of theuser's field of view.

Concurrently, light ray 435 propagates down and to the left near axis401 and diffracts from gratings in the lower portion of the waveguidenear axis 401, producing light ray 436, which propagates up and to theleft. Light ray 436 propagates in the waveguide and diffracts fromgratings in the upper portion of the waveguide near axis 401, producingoutcoupling event 437. Outcoupled light ray 438 is illustrated aspropagating down toward the user from the upper portion of the waveguidenear axis 401, thereby producing a lower portion of the field of view.As will be evident to one of skill in the art, rays incoupled atintermediate angles and operable to propagate in the waveguide will fillout the field of view. Referring to FIG. 4C, field of view 460 isproduced by the light rays illustrated by light rays 431 and 435.

FIG. 4C is a simplified k-space diagram illustrating operation of theeyepiece waveguide illustrated in FIG. 4A. Referring to FIG. 4C, acombined field of view including four fields of view is formed by theoverlap between field of view 410 and field of view 430, which areproduced by light incident from a first projector, and field of view 460and field of view 470, which are produced by light incident from asecond projector.

As illustrated in FIG. 4C, each of the individual fields of view have aspatial extent of ˜50° vertically by ˜40° horizontally. By combiningfour individual fields of view in a combined field of view, the overlapbetween these fields of view results in a combined field of viewcharacterized by a much larger extended field of view of ˜80°×˜100°.Thus, using embodiments of the present invention that utilize twoprojectors and gratings that are characterized by increased gratingperiod in two dimensions, waveguide displays with an increased orextended field of view are enabled.

Referring to FIG. 4C, embodiments of the present invention providedisplays with a tiled field of view that is formed by tiling multipleindividual fields of view, with or without overlap between adjacentfields of view. As will be evident to one of skill in the art, in thisembodiment of an eyepiece waveguide fabricated in a polymer with anindex of 1.75, the annulus defined by the circle positioned at n=1.0 andthe circle positioned at n=1.75 corresponds to the in-waveguide angles.It will be appreciated that embodiments of the present invention, incontrast with designs that utilize expensive and exotic materials suchas sapphire and lithium niobate, provide eyepiece waveguides that can befabricated in low cost, low weight, and robust low refractive indexmaterials such as polymers while still providing a large field of viewin a combined field of view design. Although some of the discussionherein is related to polymer materials, embodiments of the presentinvention are not limited to these materials and the concepts discussedherein are applicable to materials with indices of refraction greaterthan 1.75. In particular, the annulus having a boundary at n=1.75 is notintended to limit the scope of the present invention. One of ordinaryskill in the art would recognize many variations, modifications, andalternatives.

The k-space diagram in FIG. 4C demonstrates that the eyepiece waveguidedesign illustrated in FIGS. 4A and 4B is characterized by an increasedgrating period along both axis 401 and axis 402 since the center offield of view 410 is translated by a distance along axis 401 and axis402 that is greater than the distance from the origin to position 419and from the origin to position 409. Thus, in the eyepiece waveguidedesign illustrated in FIGS. 4A and 4B and described by the k-spacediagram in FIG. 4C, the translation in k-space corresponding todiffraction by the ICG is greater than the distance from the origin tothe center of the annulus of in-waveguide angles. Namely, the distancein k-space from position 407 to position 409 (measured along axis 401)is greater than the distance in k-space from the origin to position 409(measured along axis 401) (i.e., increased grating period along axis401) and the distance in k-space from position 407 to position 419(measured along axis 402) is greater than the distance in k-space fromthe origin to position 419 (measured along axis 402) (i.e., increasedgrating period along axis 402).

As described more fully in relation to FIG. 3G and illustrated in FIG.4C, diffraction of light into and out of the eyepiece waveguide andpropagation of light in the eyepiece waveguide result in severaldifferent translations of field of view 410, field of view 430, field ofview 460, and field of view 470 in k-space. As illustrated in FIGS. 4Aand 4C, light diffracted from ICG 405 will translate field of view 410and field of view 430 to the right portion of the annulus ofin-waveguide angles. OPE diffraction events will translate these fieldsof view into the lower right and upper right portions of the annulus ofin-waveguide angles, respectively. Light diffracted from a grating lineoperating as an EPE event will translate these fields of view to thepositions illustrated for field of view 410 and field of view 430 in theeye-space region of the k-space diagram.

As illustrated in FIGS. 4B and 4C, light diffracted from ICG 425 willtranslate field of view 460 and field of view 470 to the left portion ofthe annulus of in-waveguide angles. OPE diffraction events willtranslate these fields of view into the lower left and upper leftportions of the annulus of in-waveguide angles, respectively. Lightdiffracted from a grating line operating as an EPE event will translatethese fields of view to the positions illustrated for field of view 460and field of view 470 in the eye-space region of the k-space diagram.

As illustrated in FIG. 4C, the centers of each of the fields of view areoffset from the origin of the k-space diagram. As discussed herein, theuse of gratings having increased period in both directions results inthis vertical and horizontal offset. As a result, by using twoprojectors, one providing image light to a first ICG and one providingimage light to a second ICG, an extended field of view can be created bythe tiling of the individual fields of view, with the overlap betweenthe individual fields of view being defined by the gratingcharacteristics.

It should be noted that the description provided in relation to FIGS. 4Aand 4B relates to the central ray that would be associated with thecentral pixel of the projected image frame. In addition, rays that areformed at the edges of the image frame can be analyzed using theformalism utilized above in relation to FIGS. 4A and 4B. These rays canbe referred to as peripheral rays. As will be evident to one of skill inthe art, propagation in the k-space diagram is inversely related topropagation in image space, with propagation in the upper portion of thek-space diagram corresponding to propagation in the lower portion of theimage space. As illustrated in FIGS. 4A-4C, light rays outcoupled fromthe bottom portion the eyepiece waveguide along an upward direction willbe directed toward the eyebox in a manner suitable for reaching theuser's pupil when it is well-centered with respect to the eyepiecewaveguide. Furthermore, light rays outcoupled from the top portion theeyepiece waveguide along a downward direction will be directed towardthe eyebox in a manner suitable for reaching the user's pupil when it iswell-centered with respect to the eyepiece waveguide. Accordingly,embodiments of the present invention provide efficient designs in whichlight is outcoupled in a manner that preferentially reaches the user'spupil when the pupil is well-centered in the eyebox.

By tracking peripheral rays that are associated with the top of thefield of view, the bottom of the field of view, and the sides of thefield of view of each image frame, the inventors have demonstrated thatthe rays that correspond to the bottom of the field of view areoutcoupled efficiently at the bottom of the eyepiece waveguide, withreduced or minimal outcoupling at the top of the eyepiece waveguide.Accordingly, light efficiency in reaching the eyebox and the pupil ofthe user's eye is increased by embodiments of the present inventionsince the outcoupling events are increased and/or maximized for lightfrom the projector providing light to ICG 405 that is outcoupled fromthe bottom of the eyepiece waveguide along an upward direction that isdirected toward the eyebox and outcoupling events are increased and/ormaximized for light from the projector providing light to ICG 425 thatis outcoupled from the top of the eyepiece waveguide along a downwarddirection that is directed toward the eyebox.

FIG. 4D is a simplified flowchart illustrating a method of operating aneyepiece waveguide defined by a first region and a second regionaccording to an embodiment of the present invention. The methodillustrated in FIG. 4D can be implemented in the context of themulti-projector waveguide display utilizing an eyepiece waveguideillustrated in FIGS. 4A and 4B. The method 480 includes directing lightfrom a first projector to impinge on a first incoupling grating (ICG)(482). The first projector, illustrated as projector 621 in FIG. 6A, canproject light that impinges on first ICG illustrated as ICG 405 in FIG.4A or ICG 620 in FIG. 6A.

Light incident on the first ICG is diffracted into the plane of theeyepiece waveguide and a fraction of the light from the first projectoris diffracted into a first portion of the first region of the eyepiecewaveguide, into a first portion of the second region, into a secondportion of the second region, and out of the eyepiece waveguide (484).Referring to FIG. 4A, light diffracted into the first portion of thefirst region 403 of the eyepiece waveguide passes into the first portionof the second region 404 without diffraction, whereas, in FIG. 6A, lightdiffracted into the first portion 602 of the first region 601 of theeyepiece waveguide is diffracted in the plane of the eyepiece waveguidetoward the first portion 605 of the second region 604. Thus, in someembodiments, the first portion of the first region of the eyepiecewaveguide includes a first set of diffractive optical elements, e.g., afirst set of gratings that are blazed and characterized by decreasedoutcoupling efficiency for light from the first projector.

As light propagates in the first portion of the second region of theeyepiece waveguide, diffraction from diffractive optical elements, e.g.,gratings, results in redirection of the light toward the second portionof the second region 404, illustrated by light ray 412 in FIG. 4A. Thegratings in the first portion of the second region can be oriented at˜150° to the axis passing between ICG 405 and ICG 425. Additionally,light ray 412 illustrated in FIG. 4A propagates in the waveguide anddiffracts from gratings in the second portion of the second region,producing outcoupling out of the eyepiece waveguide. The gratings in thesecond portion of the second region can be oriented at ˜150° to the axispassing between ICG 405 and ICG 425. As described in relation to FIG.4A, the outcoupled light ray propagates up toward the user from thesecond portion of the second region of the waveguide, thereby producinga portion of the field of view associated with the lower portion of theuser's field of view.

Another fraction of the light from the first projector is diffractedinto the second portion of the first region of the eyepiece waveguide,into the second portion of the second region, into the first portion ofthe second region, and out of the eyepiece waveguide (486). Referring toFIG. 4A, light diffracted into the second portion of the first region403 of the eyepiece waveguide passes into the second portion of thesecond region 404 without diffraction, whereas, in other embodiments,light diffracted into the second portion of the first region of theeyepiece waveguide is diffracted in the plane of the eyepiece waveguidetoward the second portion of the second region. Thus, in someembodiments, the second portion of the first region of the eyepiecewaveguide includes a second set of diffractive optical elements, e.g., asecond set of gratings that are blazed and characterized by decreasedoutcoupling efficiency for light from the first projector.

As light propagates in the second portion of the second region of theeyepiece waveguide, diffraction from diffractive optical elements, e.g.,gratings, results in redirection of the light toward the first portionof the second region 404, illustrated by light ray 416 in FIG. 4A. Thegratings in the first portion of the first region can be oriented at˜30° to the axis passing between ICG 405 and ICG 425. Additionally,light ray 416 illustrated in FIG. 4A propagates in the waveguide anddiffracts from gratings in the first portion of the second region 404,producing outcoupling out of the eyepiece waveguide. The gratings in thesecond portion of the first region can be oriented at ˜−30° to the axispassing between ICG 405 and ICG 425. As described in relation to FIG.4A, the outcoupled light ray propagates down toward the user from thefirst portion of the second region of the waveguide, thereby producing aportion of the field of view associated with the upper portion of theuser's field of view.

The method also includes directing light from a second projector toimpinge on a second incoupling grating (ICG) (488). The secondprojector, illustrated as second projector 626 in FIG. 6A, can projectlight that impinges on second ICG illustrated as ICG 425 in FIG. 4A orICG 625 in FIG. 6A.

Light incident on the second ICG is diffracted into the plane of theeyepiece waveguide and a fraction of the light from the second projectoris diffracted into a first portion of the second region of the eyepiecewaveguide, into the first portion of the first region, into a secondportion of the first region, and out of the eyepiece waveguide (490).Referring to FIG. 4B, light diffracted into the first portion of thesecond region 404 of the eyepiece waveguide passes into the firstportion of the first region 403 without diffraction, whereas, in otherembodiments, light diffracted into the first portion of the secondregion of the eyepiece waveguide is diffracted in the plane of theeyepiece waveguide toward the first portion of the first region. Thus,in some embodiments, the first portion of the second region of theeyepiece waveguide includes a third set of diffractive optical elements,e.g., a third set of gratings that are blazed and characterized bydecreased outcoupling efficiency for light from the second projector.

As light propagates in the first portion of the first region of theeyepiece waveguide, diffraction from diffractive optical elements, e.g.,gratings, results in redirection of the light toward the second portionof the first region, illustrated by light ray 432 in FIG. 4B. Thegratings in the first portion of the first region can be oriented at˜30° to the axis passing between ICG 405 and ICG 425. Additionally,light ray 432 illustrated in FIG. 4B propagates in the waveguide anddiffracts from gratings in the second portion of the first region,producing outcoupling out of the eyepiece waveguide. The gratings in thesecond portion of the first region can be oriented at ˜30° to the axispassing between ICG 405 and ICG 425. As described in relation to FIG.4B, the outcoupled light ray propagates up toward the user from thesecond portion of the first region of the waveguide, thereby producing aportion of the field of view associated with the lower portion of theuser's field of view.

Another fraction of the light from the second projector is diffractedinto the second portion of the second region of the eyepiece waveguide,into the second portion of the first region, into the first portion ofthe first region, and out of the eyepiece waveguide (492). Referring toFIG. 4B, light diffracted into the second portion of the second regionof the eyepiece waveguide passes into the second portion of the firstregion without diffraction, whereas, in other embodiments, lightdiffracted into the second portion of the second region of the eyepiecewaveguide is diffracted in the plane of the eyepiece waveguide towardthe second portion of the first region. Thus, in some embodiments, thesecond portion of the second region of the eyepiece waveguide includes afourth set of diffractive optical elements, e.g., a fourth set ofgratings that are blazed and characterized by decreased outcouplingefficiency for light from the second projector.

As light propagates in the second portion of the first region of theeyepiece waveguide, diffraction from diffractive optical elements, e.g.,gratings, results in redirection of the light toward the first portionof the first region, illustrated by light ray 436 in FIG. 4B. Thegratings in the second portion of the first region can be oriented at˜−30° to the axis passing between ICG 405 and ICG 425. Additionally,light ray 436 illustrated in FIG. 4B propagates in the waveguide anddiffracts from gratings in the first portion of the first region,producing outcoupling out of the eyepiece waveguide. The gratings in thefirst portion of the first region can be oriented at ˜30° to the axispassing between ICG 405 and ICG 425. As described in relation to FIG.4B, the outcoupled light ray propagates down toward the user from thefirst portion of the first region of the waveguide, thereby producing aportion of the field of view associated with the upper portion of theuser's field of view.

In some embodiments, the light from the first projector impinges on thefirst ICG at a first non-zero angle of incidence and the light from thesecond projector impinges on the second ICG at a second non-zero angleof incidence equal to zero minus the first non-zero angle of incidence.In these embodiments, a first field of view of the first portion of thesecond region is centered at the non-zero angle of incidence and asecond field of view of the first portion of the first region iscentered at the non-zero angle of incidence.

It should be appreciated that the specific steps illustrated in FIG. 4Dprovide a particular method of operating an eyepiece waveguide definedby a first region and a second region according to an embodiment of thepresent invention. Other sequences of steps may also be performedaccording to alternative embodiments. For example, alternativeembodiments of the present invention may perform the steps outlinedabove in a different order. Moreover, the individual steps illustratedin FIG. 4D may include multiple sub-steps that may be performed invarious sequences as appropriate to the individual step. Furthermore,additional steps may be added or removed depending on the particularapplications. One of ordinary skill in the art would recognize manyvariations, modifications, and alternatives.

FIG. 5A is a simplified plan view diagram illustrating a multi-projectorwaveguide display utilizing an eyepiece waveguide with decreased gratingperiod according to an embodiment of the present invention. Thedescription provided in relation to FIGS. 4A-4C is applicable to FIGS.5A-5C, but for eyepiece waveguides with decreased grating period.

In this design in which the grating period is decreased by increasingthe grating pitch, light is outcoupled after propagating a reduceddistance along the eyepiece waveguide. Referring to FIG. 5A, lightincident on ICG 505 is outcoupled in field of view 510 of the eyepiecewaveguide adjacent ICG 505. Similarly, light incident on ICG 525 isoutcoupled in field of view 530 of the eyepiece waveguide adjacent ICG525.

FIG. 5B is a simplified k-space diagram illustrating operation of theeyepiece waveguide illustrated in FIG. 5A.

The k-space diagram in FIG. 5B demonstrates that the eyepiece waveguidedesign illustrated in FIG. 5A is a design characterized by a decreasedgrating period along axis 501 and an increased grating period along axis502. The decreased grating period along axis 501 is illustrated by thecenter of field of view 510/560 being translated by a distance alongaxis 501 that is less than the distance from the origin to the center ofthe annulus of in-waveguide angles. Similarly, the center of field ofview 530/570 is translated by a distance along axis 501 that is lessthan the distance from the origin to the center of the annulus ofin-waveguide angles. In the vertical direction aligned with axis 502,behavior similar to that discussed above in relation to FIG. 4C isdemonstrated. Accordingly, the center of field of view 510/560 istranslated by a distance along axis 502 that is greater than thedistance from the origin to the center of the annulus of in-waveguideangles. Similarly, the center of field of view 530/570 is translated bya distance along axis 501 that is greater than the distance from theorigin to the center of the annulus of in-waveguide angles.

As illustrated in FIG. 5B, the field of view achieved using the eyepiecewaveguide design illustrated in FIG. 5A can reach a field of view alonga first direction of ˜50° to about ˜180° at the furthest extent by ˜50°in a second direction orthogonal to the first direction. It should benoted that the combination of fields of view 510 and 560 in the upperportion of the k-space diagram and fields of view 530 and 570 in thelower portion of the k-space diagram result in a notch in region 575that may be masked as appropriate to the particular application.

FIG. 6A is a simplified plan view illustrating elements of amulti-projector waveguide display according to an embodiment of thepresent invention. As illustrated in FIG. 6A and described more fullybelow, eyepiece waveguide 600, which can also be referred to as awaveguide display component, includes ICG 620, which can be referred toas a first ICG. ICG 620 is operable to receive input light from firstprojector 621. As discussed in relation to FIG. 1, ICG 620 receivesinput light propagating along a direction having a component alignedwith the z-axis, i.e., normal to the input surface of eyepiece waveguide600, which lies in the x-y plane, and couples at least a portion of theinput light into the waveguide.

Eyepiece waveguide 600 also includes ICG 625, which can be referred toas a second ICG. ICG 625 is operable to receive input light from secondprojector 626. As discussed in relation to FIG. 1, ICG 620 receivesinput light propagating along a direction having a component alignedwith the z-axis, i.e., normal to the input surface of eyepiece waveguide600, which lies in the x-y plane, and couples at least a portion of theinput light into the waveguide.

ICG 620 and ICG 625 are disposed along the x-axis, which lies in theplane of the eyepiece waveguide. Referring to FIG. 6A, waveguide display600 further includes multiple regions in which light is diffracted inthe plane of the waveguide display as well as out of the plane of thewaveguide display. These multiple regions include first region 601 andsecond region 604. In each region, the grating lines or otherdiffractive structures present in the portions of the region areoriented at a predetermined angle with respect to other grating linespresent in other portions of the region or with respect to grating linesin the other region (or others of multiple regions).

It should be noted that in the two projector designs illustrated inFIGS. 6A and 6B gratings in a portion of a region can perform differentdiffractive functions depending on the source of the light incident onthe gratings. As an example, light incident on ICG 620, when propagatingin second portion 606 of second region 604, can interact with gratingsin second portion 606 to outcouple from the eyepiece waveguide. That is,gratings in second portion 606 can function as EPE gratings for lightfrom projector 621. In contrast, light incident on ICG 625, whenpropagating in second portion 606 of second region 604, can interactwith gratings in second portion 606 to diffract in the plane of theeyepiece waveguide toward first portion 605. That is, gratings in secondportion 606 can function as OPE gratings for light from second projector626. Similar diverse effects will be evident for other gratings in otherportions, resulting in different functionality (i.e., OPE or EPEfunctionality) depending on the source of the light propagating in theeyepiece waveguide. One of ordinary skill in the art would recognizemany variations, modifications, and alternatives.

In contrast with the areas of second portion 606 having only a singleset of gratings, the overlap region 630 between first region 601 andsecond region 604 will produce multiple effects, for example, both EPEand OPE effects. Because multiple sets of gratings are present,diffraction effects will be produced for light incident from bothprojectors.

The actual implementation used to provide gratings in first portion 602and second portion 603 of first region 601 and first portion 605 andsecond portion 606 of second region 604 can be varied. As an example,gratings in second portion 603 of first region 601 and first portion 605of second region 604 (i.e., the gratings oriented at −30° to the x-axis)can be formed on a first surface of the substrate used to fabricate theeyepiece waveguide and gratings in first portion 602 of first region 601and second portion 606 of second region 604 (i.e., the gratings orientedat 30° to the x-axis) can be formed on a second surface of the substrateopposing the first surface. Thus, overlap region 630 can be formed fromgratings present on both surfaces of the eyepiece waveguide.

FIG. 6B is a simplified plan view diagram illustrating propagation oflight rays in a multi-projector waveguide display according to anembodiment of the present invention.

Referring to FIGS. 6A and 6B, first region 601 includes a first portion602, also referred to as an upper portion or a top portion, that ischaracterized by grating lines 616 oriented at an angle of ˜30° to thex-axis, along which ICG 620 and ICG 625 lie. First region 601 alsoincludes a second portion 603, also referred to as a lower portion or abottom portion, that is characterized by grating lines 618 oriented atan angle of ˜−30° to the x-axis. As a result, grating lines 616 andgrating lines 618 are oriented at an angle of ˜60° to each other. Aswill be evident to one of skill in the art, the spacing between gratinglines 616 and 618 is not drawn to scale for purposes of clarity.

Second region 604 includes a first portion 605, also referred to as anupper portion or a top portion, that is characterized by grating lines629 oriented at an angle of ˜120° to the x-axis. Second region 604 alsoincludes a second portion 606, also referred to as a lower portion or abottom portion, that is characterized by grating lines 628 oriented atan angle of ˜−120° to the x-axis. As a result and in a manner similar tofirst region 601, grating lines 629 and grating lines 628 in secondregion 604 are oriented at an angle of ˜60° to each other. As will beevident to one of skill in the art, the spacing between grating lines629 and 628 is not drawn to scale for purposes of clarity.

In overlap region 630, grating lines 616 overlap with grating lines 629and grating lines 618 overlap with grating lines 628. Thus, in additionto portions including a single set of grating lines, overlap region 630includes multiple sets of overlapping grating lines and can be referredto as an intersection region. This overlap region enables a designer toimplement a design with a larger exit pupil and balance efficiency ofoperation of the eyepiece waveguide with increases in exit pupil size,which is more tolerant of motion of the user's eye pupil.

Although grating lines 616 in first portion 602 of first region 601 andgrating lines 618 in second portion 603 of first region 601 areillustrated as intersecting at the x-axis with no overlap of gratinglines 616 in the second portion 603 and grating lines 618 in the firstportion 602, this is not required by embodiments of the presentinvention. In some embodiments, grating lines 616 extend into secondportion 603 and grating lines 618 extend into first portion 602.

As described more fully herein, the presence of the grating lines in thedifferent portions of first region 601 and second region 604, includingoverlap of the grating lines in overlap region 630, enables the gratinglines to function as an orthogonal pupil expander (OPE), diffractinglight propagating in the plane of the eyepiece waveguide into newpropagating directions and expanding the lateral dimension of lightpropagating in the eyepiece waveguide, as well as an exit pupil expander(EPE), diffracting light propagating in the plane of the eyepiecewaveguide out of the plane of the eyepiece waveguide. Of particular noteis that, depending on the direction in which light is propagating in theeyepiece waveguide, a set of grating lines can function as either an OPEor an EPE. As an example, for a given set of grating lines, lightpropagating in a first direction can be diffracted in the plane of theeyepiece waveguide (OPE functionality) while light propagating in asecond direction orthogonal to the first direction can be diffracted outof the plane of the eyepiece waveguide (EPE functionality).

Referring to FIGS. 6A and 6B, as light propagates through first portion602 of first region 601, interaction with grating lines 616 results indiffraction in the plane of the eyepiece waveguide along the directionof the axis between the ICGs. As a result of this diffraction, analogousto OPE diffraction, multiple copies of the first copy of the image areformed and propagate in the direction aligned with this axis.

Light propagating from first portion 602 to overlap region 630, becauseof the presence of grating lines oriented at of ˜30° to the x-axis aswell as grating lines oriented at ˜120° to the x-axis, experiencesdiffraction in multiple directions in the plane of the eyepiecewaveguide as well as out of the plane of the eyepiece waveguide. Lightpropagating in the direction aligned with the x-axis will encountergrating lines 629 and will diffract along the direction illustrated byarrow 627 in the plane of the eyepiece waveguide. As the lightpropagates along this direction, the light will encounter grating lines628 and will experience an outcoupling event from the eyepiecewaveguide. These outcoupling events are illustrated in FIG. 6B by opencircles.

Referring to first portion 605, light propagating in the directionaligned with the x-axis passes through overlap region 630, encountersgrating lines 629, and diffracts along the direction of arrow 627 in theplane of the eyepiece waveguide. Laddering of the light during thesediffraction events will occur as appropriate to OPE functionality. Asthe light propagates further along the direction of arrow 627, the lightwill enter second portion 606, encounter grating lines 628, andexperience additional outcoupling events from the eyepiece waveguide.These outcoupling events, like the outcoupling events produced inoverlap region 630, are illustrated in FIG. 6B by open circles.

Thus, light entering the eyepiece waveguide at ICG 620 and generated bya first projector 621 can be outcoupled in second region 604. In thedesign illustrated in FIGS. 6A and 6B, light coupled into the eyepiecewaveguide at ICG 620 preferably passes through first region 601 withoutexperiencing outcoupling events, thereby resulting in little to no lightloss by outcoupling, with passage through first region 601 onlyresulting in diffraction in the plane of the eyepiece waveguide,replicating OPE functionality. As a result, all outcoupling events forlight from the first projector are preferably experienced in secondregion 604, which provides an output that forms one of the sub-displaysof the combined display. Because, as illustrated in FIG. 2B, the cone oflight rays entering the ICG was centered at a non-normal angle ofincidence, the cone of light rays outcoupled in second region 604 alsopropagates at a non-normal angle of incidence, enabling spatialseparation between the sub-displays and tiling of the combined display.

In addition to light entering ICG 620, light entering ICG 625 willundergo similar interactions as it propagates through second region 604,resulting in OPE interactions, and experiencing EPE interactions infirst region 601. One of ordinary skill in the art would recognize manyvariations, modifications, and alternatives.

FIG. 7A is a simplified plan view diagram illustrating a six-projectorwaveguide display according to an embodiment of the present invention.In the six-projector design illustrated in FIG. 7A, six projectors aredisposed at 60° angles around the periphery of the eyepiece waveguide.The six-projector waveguide display illustrated in FIG. 7A is a designutilizing a decreased grating period.

Light from six projectors (not shown) is coupled into a shared eyepiecewaveguide region via ICGs 710, 713, 714, 716, 718, and 720. The sharedeyepiece waveguide region includes three different grating vectorsincluding grating vector 722 aligned with an axis passing through aperpendicular bisector of the line connecting ICGs 713 and 714 and aperpendicular bisector of the line connecting ICGs 718 and 720, i.e.,vertically oriented axis 702, grating vector 724 aligned with an axispassing through a perpendicular bisector of the line connecting ICGs 710and 720 and a perpendicular bisector of the line connecting ICGs 714 and716, i.e., an axis oriented at −30° to vertical axis 702, and gratingvector 726 aligned with an axis passing through a perpendicular bisectorof the line connecting ICGs 716 and 718 and a perpendicular bisector ofthe line connecting ICGs 710 and 713, i.e., an axis oriented at +30° tovertical axis 702.

Referring to ICG 710, light incoupled via ICG 710 propagates in regions712 and 719 along directions having a component aligned with axis 701.Regions 712 and 719 utilize a design similar to that shown in FIG. 5A,i.e., a chevron design in which gratings in region 712 are tilted at anangle of −120° to horizontal axis 701 and gratings in region 719 aretilted at an angle of 120° to horizontal axis 701. Light associated withthe bottom of the field of view propagates through region 719,experiences diffraction toward region 712 (e.g., with little to nooutcoupling), and is outcoupled from region 712. Similarly, lightassociated with the top of the field of view propagates through region712, experiences diffraction toward region 719 (e.g., with little to nooutcoupling), and is outcoupled from region 719. Additional descriptionrelated to these interactions is provided in relation to FIG. 7B.

Utilizing the six-projector design illustrated in FIG. 7A, including sixincoupling gratings and a shared eyepiece waveguide region, a combined,conical field of view of ˜100° is achieved in a polymer eyepiece havingan index of refraction of ˜1.75.

FIG. 7B is a simplified plan view diagram illustrating a singleprojector element of the six-projector waveguide display illustrated inFIG. 7A. FIG. 7C is a simplified k-space diagram illustrating operationof the single projector element illustrated in FIG. 7B. Referring toFIGS. 7B and 7C, light diffraction and accompanying translation of thefield of view in k-space can be described. As illustrated in FIG. 7B, aportion of light diffracted from ICG 710 can be represented by light ray740 as light propagates into region 712. Diffraction from gratings inregion 712 will result in generation of light ray 741 directed towardthe top half of the waveguide, i.e., region 719. This can be consideredas an OPE event.

After propagating into the top half of the waveguide, i.e., region 719,diffraction from gratings in region 719 will result in generation ofoutput light ray 742 propagating down toward the user, representinglight in the upper portion of the user's field of view.

Similarly, light in the lower portion of the user's field of view willbe produced as light ray 750 propagates into the top half of thewaveguide, i.e., region 719, after diffraction from ICG 710. Diffractionfrom gratings into the top half of the waveguide, i.e., region 719, willresult in the generation of light ray 751 (an OPE event), whichpropagates into the lower half of the waveguide, i.e., region 712.Diffraction as an EPE event in region 712 will result in the generationof output light ray 752 propagating up toward the user.

It should be noted that although the shared eyepiece waveguide regionillustrated in FIGS. 7A and 7B only includes overlap between adjacentgrating vectors in the central region at which the grating linesoverlap. In other embodiments, the overlap region can extend closer toeach of the respective ICGs. These designs with increased overlap enableperformance in which, if the user's pupil moves in the eyebox to aposition off-center from the center of the eyebox, the visibility of thefield of view is more tolerant to this deviation of the user's pupilfrom a well-centered pupil location, which may result from a change inthe user's gaze.

Referring to FIG. 7C, diffraction from the ICG 710 corresponds totranslation of field of view 730 to position 732. Diffraction fromgratings in region 719 (OPE event) represented by light ray 751 resultsin translation of the field of view to position 734 and diffraction inregion 712 (EPE event) results in translation of the field of view tothe eye-space region of the k-space diagram.

Similarly, diffraction from gratings in region 712 (OPE event)represented by light ray 741 results in translation of the field of viewto position 736 and diffraction in region 719 (EPE event) results intranslation of the field of view to the eye-space region of the k-spacediagram.

The k-space diagram in FIG. 7C demonstrates that the eyepiece waveguidedesign illustrated in FIG. 7B utilizes gratings with a decreased gratingperiod along axis 701 since the center of field of view 730 istranslated along axis 701 by a distance that is less than the distancefrom the origin to the annulus of in-waveguide angles.

FIG. 7D is a simplified k-space diagram illustrating operation of thesix-projector waveguide display illustrated in FIG. 7A. When theanalysis performed for the portion of the six-projector waveguidedisplay that is illustrated in FIG. 7B is extended to the five otherprojectors, a combined field of view including six partially overlappingfields of view is produced as shown in FIG. 7D. This combined field ofview is formed by tiling individual fields of view that are a generallycone-shaped sector with a circular termination results in a combinedfield of view that is circular and characterized by a combined, conicalfield of view of ˜100° in a polymer eyepiece having an index ofrefraction of ˜1.75.

FIG. 8 is a simplified perspective drawing illustrating integration ofglasses and one or more eyepiece waveguides according to embodiments ofthe present invention. As illustrated in FIG. 8, eyepiece waveguides canbe integrated into the right lens frame 801 and the left lens frame 802of a pair of glasses. The integration of a first eyepiece waveguide 830in right lens frame 801 and a second eyepiece waveguide 840 in left lensframe 802 enables a wide field of view as a result of the functionalityof eyepiece waveguides described herein. As illustrated in FIG. 8, firstwaveguide display 805 utilizes two eyepiece waveguides 830 and 840,which each include ICG 832/842, and CPE 834/844.

It is also understood that the examples and embodiments described hereinare for illustrative purposes only and that various modifications orchanges in light thereof will be suggested to persons skilled in the artand are to be included within the spirit and purview of this applicationand scope of the appended claims.

What is claimed is:
 1. An eyepiece waveguide for an augmented realitydisplay system, the eyepiece waveguide comprising: a substrate having afirst surface and a second surface; a diffractive input coupling elementformed on or in the first surface or the second surface of thesubstrate, the diffractive input coupling element being configured toreceive an input beam of light and to couple the input beam of lightinto the substrate as a guided beam; and a diffractive combined pupilexpander-extractor (CPE) element formed on or in the first surface orthe second surface of the substrate, wherein the diffractive CPE elementincludes a first portion and a second portion divided by an axis,wherein: a first set of diffractive optical elements disposed in thefirst portion and oriented at a positive angle with respect to the axis;and a second set of diffractive optical elements disposed in the secondportion and oriented at a negative angle with respect to the axis. 2.The eyepiece waveguide of claim 1 wherein the positive angle is ˜30° andthe negative angle is ˜−30°.
 3. The eyepiece waveguide of claim 1wherein the first set of diffractive optical elements comprises a firstset of gratings and the second set of diffractive optical elementscomprises a second set of diffraction gratings.
 4. The eyepiecewaveguide of claim 1 wherein the first set of diffractive opticalelements extends into the second portion and the second set ofdiffractive optical elements extends into the first portion to form anoverlap region.
 5. The eyepiece waveguide of claim 4 wherein the overlapregion is centered on the axis.
 6. The eyepiece waveguide of claim 5wherein the axis passes through the diffractive input coupling element.7. The eyepiece waveguide of claim 1 wherein the input beam of lightimpinges on the diffractive input coupling element at a non-zero angleof incidence.
 8. The eyepiece waveguide of claim 7 wherein thediffractive input coupling element is characterized by a grating periodsuch that a cone of rays incoupled by the diffractive input couplingelement is centered on an axis parallel to the substrate.
 9. An eyepiecewaveguide for an augmented reality display system, the eyepiecewaveguide comprising: a substrate having a first surface and a secondsurface; a first diffractive input coupling element formed on or in thefirst surface or the second surface of the substrate, the firstdiffractive input coupling element being configured to receive a firstinput beam of light and to couple the first input beam of light into thesubstrate as a first guided beam; a second diffractive input couplingelement formed on or in the first surface or the second surface of thesubstrate, the second diffractive input coupling element beingconfigured to receive a second input beam of light and to couple thesecond input beam of light into the substrate as a second guided beam; adiffractive combined pupil expander-extractor (CPE) element formed on orin the first surface or the second surface of the substrate, thediffractive CPE element being positioned to: receive the first guidedbeam from the first diffractive input coupling element; receive thesecond guided beam from the second diffractive input coupling element;outcouple at least a portion of the first guided beam over a first rangeof angles to form a first field of view of a combined field of view; andoutcouple at least a portion of the second guided beam over a secondrange of angles to form a second field of view of the combined field ofview.
 10. The eyepiece waveguide of claim 9 wherein the diffractive CPEelement comprises a first set of gratings disposed in a first portion ofa first region oriented at ˜30° to an axis and a second set of gratingsdisposed in a second portion of the first region oriented at ˜−30° tothe axis.
 11. The eyepiece waveguide of claim 10 wherein the diffractiveCPE element comprises a third set of gratings disposed in a firstportion of a second region oriented at ˜150° to the axis and a fourthset of gratings disposed in a second portion of the second regionoriented at ˜−150° to the axis.
 12. The eyepiece waveguide of claim 9wherein the first input beam of light is incident on the substrate at anon-normal angle of incidence and the first field of view of thecombined field of view is centered at the non-normal angle of incidence.13. The eyepiece waveguide of claim 12 wherein the second input beam oflight is incident on the substrate at zero minus the non-normal angle ofincidence and the second field of view of the combined field of view iscentered at zero minus the non-normal angle of incidence.
 14. Theeyepiece waveguide of claim 9 wherein the first field of view and thesecond field of view are tiled.
 15. The eyepiece waveguide of claim 14wherein a portion of the first field of view overlaps with a portion ofthe second field of view.
 16. A waveguide display disposed in glasses,the waveguide display comprising: a first projector; a second projector;a first incoupling grating (ICG) optically coupled to the firstprojector; a second ICG optically coupled to the second projector,wherein an axis passes through the first ICG and the second ICG; a firstdiffractive region optically coupled to the first ICG and including: afirst portion comprising a first set of gratings oriented at a positiveangle with respect to the axis; and a second portion comprising a secondset of gratings oriented at a negative angle with respect to the axis;and a second diffractive region optically coupled to the second ICG andincluding: a first portion comprising a third set of gratings orientedat 180° minus the positive angle with respect to the axis; and a secondportion comprising a fourth set of gratings oriented at −180° minus thenegative angle with respect to the axis.
 17. The waveguide display ofclaim 16 wherein the first diffractive region and the second diffractiveregion overlap to form an overlap region.
 18. The waveguide display ofclaim 17 wherein the overlap region is disposed at a midpoint betweenthe first ICG and the second ICG.
 19. The waveguide display of claim 16wherein first display light from the first projector impinges on thefirst ICG at a non-zero angle of incidence.
 20. The waveguide display ofclaim 19 wherein the first ICG is characterized by a grating period suchthat a cone of rays incoupled by the first ICG is centered on the axispassing through the first ICG and the second ICG.